Electrodynamic systems such as electric motors, generators, and alternators typically include a stator and a rotor. The stator typically has a metallic core with electrically insulated wire winding through the metallic core to form the stator coil. When current is alternately passed through a series of coils, magnetic flux fields are formed, which cause the rotor to rotate in accordance with electromagnetic physics.
Electrical submersible pumping systems include specialized electric motors that are used to power one or more high performance pump assemblies. The motor is typically an oil-filled, high capacity electric motor that can vary in length from a few feet to nearly fifty feet, and may be rated up to hundreds of horsepower. In submersible motors, the stators usually surround the rotors, which are secured to a center shaft that is used to transfer the output of the motor. In this way, the rotor and shaft spin about a common axis inside the motionless stator.
In longer submersible motors, it may be desirable to employ a number of separate rotor sections within a single stator. Each rotor section is usually constructed from a number of thin, pressed-together pieces of material, or laminations, through which ferromagnetic rods are inserted. The shaft can be secured within the inner diameter of the rotor sections with a keyed connection or by one of several other well-known methods.
When assembling a submersible motor, bearing assemblies are typically placed between adjacent rotor sections to construct a larger rotor assembly. The shaft is outfitted with one or more wear sleeves and is then inserted into the rotor assembly. The shaft and rotor assembly are then inserted into the stator. It is important that the bearing assemblies have a clearance fit within the stator. The clearance fit facilitates the sliding of the rotor assembly into the stator.
Some bearing assemblies further include an anti-rotation key designed to prevent the bearing assemblies from rotating within the stator. There is, however, no current mechanism in the prior art for preventing relative vibrational movement between the bearing assembly and the stator. Vibration in electrical motors is principally the result of imbalance in the rotating mass of the motor rotor and shaft as well as unstable orbit of the shaft within the various bearing assemblies. Such vibrations can be detrimental to the long-term reliability of the equipment. Improvements in rotor balance may reduce the risk of such electrical failures, but cannot be reliably eliminated. Even with stable shaft orbits, high vibration has still been observed in the motor housing and other components connected to the motor housing. There is, therefore, a continued need for a mechanism for stabilizing the bearing assembly relative to the other stationary components of the submersible pump. It is to these and other deficiencies in the prior art that the present invention is directed.